A. CaCO3 = ___ Ca, ___ C, ___O b. (NH4)2SO4 = ___N, ___H, ___S, ___O

c. 3 H2 = 2H d. 4 Mg(OH)2 = 4Mg, 8O,8H

e. Ba(NO3)2 = 1Ba, ___ N, ___ O

I did c on my own, is it right?? I also need help understanding the concept of this... I'm confused on the rest of the questions.